[Bug] Workflow shouldn't wait for activities unless it is explicitly said with yield

[seregazhuk]

Having such workflow, that calls activity and doesn't use (not waits) for its result (no yield keyword):

#[WorkflowMethod]
public function start()
{
    $activity = Workflow::newActivityStub(
        SleepActivity::class,
        ActivityOptions::new()->withStartToCloseTimeout(20)
    );
    $activity->wait();

    return 'Done';
}

Inside activity we have a simple sleep():

#[\Temporal\Activity\ActivityMethod]
public function wait(): void
{
    sleep(5);
}

Expected behavior: workflow finishes and doesn't wait for 5 seconds. Actual behavior: workflow waits for 5 seconds.